Hi, I turned on a few more debug options (eventually, I guess through timing/sheer chance, it becomes less likely to trigger). With lockdep, kobject, and spinlock debugging on, all I get in addition is a lockdep warning from libvirtd: virbr0: starting userspace STP failed, starting kernel STP ======================================================= [ INFO: possible circular locking dependency detected ] 2.6.33-rc5 #1 ------------------------------------------------------- libvirtd/2908 is trying to acquire lock: (s_active){++++.+}, at: [<ffffffff81168c6e>] sysfs_addrm_finish +0x36/0x55 but task is already holding lock: (rtnl_mutex){+.+.+.}, at: [<ffffffff813b618d>] rtnl_lock+0x17/0x19 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #4 (rtnl_mutex){+.+.+.}: [<ffffffff8107b8a2>] __lock_acquire+0xb71/0xd19 [<ffffffff8107bb26>] lock_acquire+0xdc/0x102 [<ffffffff8143bdae>] __mutex_lock_common+0x4b/0x392 [<ffffffff8143c1b9>] mutex_lock_nested+0x3e/0x43 [<ffffffff813b618d>] rtnl_lock+0x17/0x19 [<ffffffff813b7974>] linkwatch_event+0xe/0x2c [<ffffffff810650c8>] worker_thread+0x266/0x35f [<ffffffff8106913c>] kthread+0x9a/0xa2 [<ffffffff8100aa64>] kernel_thread_helper+0x4/0x10 -> #3 ((linkwatch_work).work){+.+.+.}: [<ffffffff8107b8a2>] __lock_acquire+0xb71/0xd19 [<ffffffff8107bb26>] lock_acquire+0xdc/0x102 [<ffffffff810650bf>] worker_thread+0x25d/0x35f [<ffffffff8106913c>] kthread+0x9a/0xa2 [<ffffffff8100aa64>] kernel_thread_helper+0x4/0x10 -> #2 (events){+.+.+.}: [<ffffffff8107b8a2>] __lock_acquire+0xb71/0xd19 [<ffffffff8107bb26>] lock_acquire+0xdc/0x102 [<ffffffff81065a01>] flush_workqueue+0x63/0xb1 [<ffffffff81065a64>] flush_scheduled_work+0x15/0x17 [<ffffffff813685ff>] do_md_stop+0x2c0/0x508 [<ffffffff8136ab07>] md_ioctl+0x92f/0xf49 [<ffffffff8120afcd>] __blkdev_driver_ioctl+0x39/0xa3 [<ffffffff8120b968>] blkdev_ioctl+0x67d/0x6b1 [<ffffffff811364e8>] block_ioctl+0x37/0x3b [<ffffffff8111d8a4>] vfs_ioctl+0x32/0xa6 [<ffffffff8111de24>] do_vfs_ioctl+0x490/0x4d6 [<ffffffff8111dec0>] sys_ioctl+0x56/0x79 [<ffffffff81009bf2>] system_call_fastpath+0x16/0x1b -> #1 (&new->reconfig_mutex){+.+.+.}: [<ffffffff8107b8a2>] __lock_acquire+0xb71/0xd19 [<ffffffff8107bb26>] lock_acquire+0xdc/0x102 [<ffffffff8143bdae>] __mutex_lock_common+0x4b/0x392 [<ffffffff8143c133>] mutex_lock_interruptible_nested+0x3e/0x43 [<ffffffff81362d1e>] mddev_lock+0x17/0x19 [<ffffffff81362ff5>] md_attr_show+0x32/0x5d [<ffffffff81167af4>] sysfs_read_file+0xbd/0x17f [<ffffffff81110ff5>] vfs_read+0xab/0x108 [<ffffffff81111112>] sys_read+0x4a/0x6e [<ffffffff81009bf2>] system_call_fastpath+0x16/0x1b -> #0 (s_active){++++.+}: [<ffffffff8107b74c>] __lock_acquire+0xa1b/0xd19 [<ffffffff8107bb26>] lock_acquire+0xdc/0x102 [<ffffffff8116867b>] sysfs_deactivate+0x9a/0x103 [<ffffffff81168c6e>] sysfs_addrm_finish+0x36/0x55 [<ffffffff81168cc3>] remove_dir+0x36/0x3e [<ffffffff81168d78>] sysfs_remove_dir+0x9d/0xbe [<ffffffff8121714b>] kobject_del+0x16/0x37 [<ffffffff81217233>] kobject_release+0xc7/0x1d9 [<ffffffff81218319>] kref_put+0x43/0x4d [<ffffffff812170c6>] kobject_put+0x47/0x4b [<ffffffffa02f6ec5>] br_sysfs_delbr+0x21/0x43 [bridge] [<ffffffffa02f30d5>] del_br+0x5a/0x6f [bridge] [<ffffffffa02f349e>] br_del_bridge+0x59/0x67 [bridge] [<ffffffffa02f4740>] br_ioctl_deviceless_stub+0x1fb/0x21b [bridge] [<ffffffff8139a7d5>] sock_ioctl+0x141/0x20d [<ffffffff8111d8a4>] vfs_ioctl+0x32/0xa6 [<ffffffff8111de24>] do_vfs_ioctl+0x490/0x4d6 [<ffffffff8111dec0>] sys_ioctl+0x56/0x79 [<ffffffff81009bf2>] system_call_fastpath+0x16/0x1b other info that might help us debug this: 2 locks held by libvirtd/2908: #0: (br_ioctl_mutex){+.+.+.}, at: [<ffffffff8139a7ba>] sock_ioctl +0x126/0x20d #1: (rtnl_mutex){+.+.+.}, at: [<ffffffff813b618d>] rtnl_lock+0x17/0x19 stack backtrace: Pid: 2908, comm: libvirtd Not tainted 2.6.33-rc5 #1 Call Trace: [<ffffffff8107a90f>] print_circular_bug+0xa8/0xb6 [<ffffffff8107b74c>] __lock_acquire+0xa1b/0xd19 [<ffffffff8107bb26>] lock_acquire+0xdc/0x102 [<ffffffff81168c6e>] ? sysfs_addrm_finish+0x36/0x55 [<ffffffff810795fe>] ? lockdep_init_map+0x9e/0x113 [<ffffffff8116867b>] sysfs_deactivate+0x9a/0x103 [<ffffffff81168c6e>] ? sysfs_addrm_finish+0x36/0x55 [<ffffffff81078d72>] ? trace_hardirqs_off+0xd/0xf [<ffffffff8143bbcd>] ? __mutex_unlock_slowpath+0x120/0x132 [<ffffffff81168c6e>] sysfs_addrm_finish+0x36/0x55 [<ffffffff81168cc3>] remove_dir+0x36/0x3e [<ffffffff81168d78>] sysfs_remove_dir+0x9d/0xbe [<ffffffff8121714b>] kobject_del+0x16/0x37 [<ffffffff81217233>] kobject_release+0xc7/0x1d9 [<ffffffff8121716c>] ? kobject_release+0x0/0x1d9 [<ffffffff81218319>] kref_put+0x43/0x4d [<ffffffff812170c6>] kobject_put+0x47/0x4b [<ffffffff8105b24c>] ? del_timer_sync+0x0/0xa6 [<ffffffffa02f6ec5>] br_sysfs_delbr+0x21/0x43 [bridge] [<ffffffffa02f30d5>] del_br+0x5a/0x6f [bridge] [<ffffffffa02f349e>] br_del_bridge+0x59/0x67 [bridge] [<ffffffffa02f4740>] br_ioctl_deviceless_stub+0x1fb/0x21b [bridge] [<ffffffff8139a7d5>] sock_ioctl+0x141/0x20d [<ffffffff8111d8a4>] vfs_ioctl+0x32/0xa6 [<ffffffff8111de24>] do_vfs_ioctl+0x490/0x4d6 [<ffffffff8111dec0>] sys_ioctl+0x56/0x79 [<ffffffff81009bf2>] system_call_fastpath+0x16/0x1b tun: Universal TUN/TAP device driver, 1.6 tun: (C) 1999-2004 Max Krasnyansky <maxk@xxxxxxxxxxxx> device vnet0 entered promiscuous mode br0: port 2(vnet0) entering forwarding state device vnet1 entered promiscuous mode br0: port 3(vnet1) entering forwarding state SELinux: initialized (dev mqueue, type mqueue), uses transition SIDs SELinux: initialized (dev proc, type proc), uses genfs_contexts SELinux: initialized (dev mqueue, type mqueue), uses transition SIDs lo: Disabled Privacy Extensions SELinux: initialized (dev proc, type proc), uses genfs_contexts vnet0: no IPv6 routers present vnet1: no IPv6 routers present TRACE: raw:PREROUTING:policy:2 IN=br0 OUT= MAC=33:33:00:00:00:16:52:54:00:75:4b:ad:86:dd SRC=0000:0000:0000:0000:0000:0000:0000:0000 DST=ff02:0000:0000:0000:0000:0000:0000:0016 LEN=76 TC=0 HOPLIMIT=1 FLOWLBL=0 OPT ( ) PROTO=ICMPv6 TYPE=143 CODE=0 TRACE: raw:PREROUTING:policy:2 IN=br0 OUT= MAC=33:33:00:00:00:16:52:54:00:75:4b:ad:86:dd SRC=0000:0000:0000:0000:0000:0000:0000:0000 DST=ff02:0000:0000:0000:0000:0000:0000:0016 LEN=76 TC=0 HOPLIMIT=1 FLOWLBL=0 OPT ( ) PROTO=ICMPv6 TYPE=143 CODE=0 TRACE: raw:PREROUTING:policy:2 IN=br0 OUT= MAC=33:33:ff:75:4b:ad:52:54:00:75:4b:ad:86:dd SRC=0000:0000:0000:0000:0000:0000:0000:0000 DST=ff02:0000:0000:0000:0000:0001:ff75:4bad LEN=64 TC=0 HOPLIMIT=255 FLOWLBL=0 PROTO=ICMPv6 TYPE=135 CODE=0 TRACE: raw:PREROUTING:policy:2 IN=br0 OUT= MAC=33:33:00:00:00:02:52:54:00:75:4b:ad:86:dd SRC=fe80:0000:0000:0000:5054:00ff:fe75:4bad DST=ff02:0000:0000:0000:0000:0000:0000:0002 LEN=56 TC=0 HOPLIMIT=255 FLOWLBL=0 PROTO=ICMPv6 TYPE=133 CODE=0 TRACE: raw:PREROUTING:policy:2 IN=br0 OUT= MAC=33:33:00:00:00:02:52:54:00:75:4b:ad:86:dd SRC=fe80:0000:0000:0000:5054:00ff:fe75:4bad DST=ff02:0000:0000:0000:0000:0000:0000:0002 LEN=56 TC=0 HOPLIMIT=255 FLOWLBL=0 PROTO=ICMPv6 TYPE=133 CODE=0 TRACE: raw:PREROUTING:policy:2 IN=br0 OUT= MAC=33:33:00:00:00:02:52:54:00:75:4b:ad:86:dd SRC=fe80:0000:0000:0000:5054:00ff:fe75:4bad DST=ff02:0000:0000:0000:0000:0000:0000:0002 LEN=56 TC=0 HOPLIMIT=255 FLOWLBL=0 PROTO=ICMPv6 TYPE=133 CODE=0 TRACE: raw:PREROUTING:policy:2 IN=br0 OUT= MAC=33:33:00:00:00:16:52:54:00:75:4b:ad:86:dd SRC=fe80:0000:0000:0000:5054:00ff:fe75:4bad DST=ff02:0000:0000:0000:0000:0000:0000:0016 LEN=76 TC=0 HOPLIMIT=1 FLOWLBL=0 OPT ( ) PROTO=ICMPv6 TYPE=143 CODE=0 TRACE: raw:PREROUTING:policy:2 IN=br0 OUT= MAC=33:33:00:00:00:16:52:54:00:75:4b:ad:86:dd SRC=fe80:0000:0000:0000:5054:00ff:fe75:4bad DST=ff02:0000:0000:0000:0000:0000:0000:0016 LEN=76 TC=0 HOPLIMIT=1 FLOWLBL=0 OPT ( ) PROTO=ICMPv6 TYPE=143 CODE=0 TRACE: raw:PREROUTING:policy:2 IN=br0 OUT= MAC=33:33:00:00:00:16:52:54:00:4c:c6:65:86:dd SRC=0000:0000:0000:0000:0000:0000:0000:0000 DST=ff02:0000:0000:0000:0000:0000:0000:0016 LEN=76 TC=0 HOPLIMIT=1 FLOWLBL=0 OPT ( ) PROTO=ICMPv6 TYPE=143 CODE=0 TRACE: raw:PREROUTING:policy:2 IN=br0 OUT= MAC=33:33:ff:4c:c6:65:52:54:00:4c:c6:65:86:dd SRC=0000:0000:0000:0000:0000:0000:0000:0000 DST=ff02:0000:0000:0000:0000:0001:ff4c:c665 LEN=64 TC=0 HOPLIMIT=255 FLOWLBL=0 PROTO=ICMPv6 TYPE=135 CODE=0 TRACE: raw:PREROUTING:policy:2 IN=br0 OUT= MAC=33:33:00:00:00:02:52:54:00:4c:c6:65:86:dd SRC=fe80:0000:0000:0000:5054:00ff:fe4c:c665 DST=ff02:0000:0000:0000:0000:0000:0000:0002 LEN=56 TC=0 HOPLIMIT=255 FLOWLBL=0 PROTO=ICMPv6 TYPE=133 CODE=0 TRACE: raw:PREROUTING:policy:2 IN=br0 OUT= MAC=33:33:00:00:00:16:52:54:00:4c:c6:65:86:dd SRC=fe80:0000:0000:0000:5054:00ff:fe4c:c665 DST=ff02:0000:0000:0000:0000:0000:0000:0016 LEN=76 TC=0 HOPLIMIT=1 FLOWLBL=0 OPT ( ) PROTO=ICMPv6 TYPE=143 CODE=0 TRACE: raw:PREROUTING:policy:2 IN=br0 OUT= MAC=33:33:00:00:00:02:52:54:00:4c:c6:65:86:dd SRC=fe80:0000:0000:0000:5054:00ff:fe4c:c665 DST=ff02:0000:0000:0000:0000:0000:0000:0002 LEN=56 TC=0 HOPLIMIT=255 FLOWLBL=0 PROTO=ICMPv6 TYPE=133 CODE=0 TRACE: raw:PREROUTING:policy:2 IN=br0 OUT= MAC=33:33:00:00:00:02:52:54:00:4c:c6:65:86:dd SRC=fe80:0000:0000:0000:5054:00ff:fe4c:c665 DST=ff02:0000:0000:0000:0000:0000:0000:0002 LEN=56 TC=0 HOPLIMIT=255 FLOWLBL=0 PROTO=ICMPv6 TYPE=133 CODE=0 TRACE: raw:PREROUTING:policy:2 IN=br0 OUT= MAC=33:33:00:00:00:16:52:54:00:4c:c6:65:86:dd SRC=fe80:0000:0000:0000:5054:00ff:fe4c:c665 DST=ff02:0000:0000:0000:0000:0000:0000:0016 LEN=76 TC=0 HOPLIMIT=1 FLOWLBL=0 OPT ( ) PROTO=ICMPv6 TYPE=143 CODE=0 TRACE: raw:PREROUTING:policy:2 IN=br0 OUT= MAC=33:33:00:00:00:16:52:54:00:4c:c6:65:86:dd SRC=fe80:0000:0000:0000:5054:00ff:fe4c:c665 DST=ff02:0000:0000:0000:0000:0000:0000:0016 LEN=76 TC=0 HOPLIMIT=1 FLOWLBL=0 OPT ( ) PROTO=ICMPv6 TYPE=143 CODE=0 device vnet2 entered promiscuous mode br0: port 4(vnet2) entering forwarding state vnet2: no IPv6 routers present BUG: unable to handle kernel paging request at ffff8805f74c8598 IP: [<ffffffff813ca6c8>] __nf_conntrack_find+0x53/0xb1 PGD 1a3c063 PUD 0 Oops: 0000 [#1] SMP last sysfs file: /sys/devices/virtual/block/md0/md/sync_speed CPU 2 Pid: 3226, comm: qemu-kvm Not tainted 2.6.33-rc5 #1 0F9382/Precision WorkStation 490 RIP: 0010:[<ffffffff813ca6c8>] [<ffffffff813ca6c8>] __nf_conntrack_find +0x53/0xb1 RSP: 0018:ffff8801b92c5768 EFLAGS: 00010282 RAX: ffff8805f74c8598 RBX: ffff8801b92c5878 RCX: 00000000b1528e8e RDX: ffff8801b9272400 RSI: 0000000081b01fa0 RDI: 0000000000000246 RBP: ffff8801b92c57a8 R08: 0000000098466e0d R09: 0000000044ad0faf R10: 00000000f1118f58 R11: ffff8801b92c589c R12: ffffffff82967ef0 R13: ffff8801b92c5878 R14: ffffffffffffffb8 R15: 000000007d1b90b3 FS: 00007f7b1d26b780(0000) GS:ffff88002fc00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b CR2: ffff8805f74c8598 CR3: 00000001baf3c000 CR4: 00000000000026e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 Process qemu-kvm (pid: 3226, threadinfo ffff8801b92c4000, task ffff8801b9272400) Stack: ffff880214fc04e0 00000003e8dc8598 ffffffffffffffb8 ffffffff82967ef0 <0> ffff880214fc04e0 ffff8801b92c5878 ffffffffffffffb8 ffffffff82967ef0 <0> ffff8801b92c57f8 ffffffff813ca759 ffff880214fc04e0 ffff880214fc04e0 Call Trace: [<ffffffff813ca759>] nf_conntrack_find_get+0x33/0xb7 [<ffffffff813cb810>] nf_conntrack_in+0x209/0x7d0 [<ffffffff8140f2b3>] ipv4_conntrack_local+0x40/0x49 [<ffffffff813c85c9>] nf_iterate+0x4d/0xab [<ffffffff813da338>] ? dst_output+0x0/0x12 [<ffffffff813c869f>] nf_hook_slow+0x78/0xe0 [<ffffffff813da338>] ? dst_output+0x0/0x12 [<ffffffff81069602>] ? autoremove_wake_function+0x24/0x39 [<ffffffff813db42a>] __ip_local_out+0x8b/0x8d [<ffffffff813db442>] ip_local_out+0x16/0x27 [<ffffffff813dba70>] ip_queue_xmit+0x30e/0x36e [<ffffffff813ed9c8>] tcp_transmit_skb+0x707/0x745 [<ffffffff813f003a>] tcp_write_xmit+0x7cb/0x8ba [<ffffffff813f018e>] __tcp_push_pending_frames+0x2f/0x5d [<ffffffff813e2dab>] tcp_push+0x88/0x8a [<ffffffff813e50cc>] tcp_sendmsg+0x760/0x85b [<ffffffff8139b42c>] __sock_sendmsg+0x5e/0x69 [<ffffffff8139b742>] sock_sendmsg+0xa8/0xc1 [<ffffffff81111999>] ? fget_light+0x57/0xf2 [<ffffffff81111940>] ? rcu_read_unlock+0x21/0x23 [<ffffffff81111999>] ? fget_light+0x57/0xf2 [<ffffffff81140cca>] ? eventfd_write+0x94/0x186 [<ffffffff8139b7d2>] ? sockfd_lookup_light+0x20/0x58 [<ffffffff8139d497>] sys_sendto+0x110/0x152 [<ffffffff81110670>] ? fsnotify_modify+0x6c/0x74 [<ffffffff81118ddf>] ? path_put+0x22/0x26 [<ffffffff810a1671>] ? audit_syscall_entry+0x11e/0x14a [<ffffffff8143cf2a>] ? trace_hardirqs_on_thunk+0x3a/0x3f [<ffffffff81009bf2>] system_call_fastpath+0x16/0x1b Code: 48 89 df e8 c9 f4 ff ff 41 89 c7 45 89 ff e8 fb 93 c8 ff 4a 8d 04 fd 00 00 00 00 48 89 45 c8 48 8b 45 c8 49 03 84 24 90 06 00 00 <4c> 8b 28 eb 14 65 83 40 04 01 e8 d0 94 c8 ff eb 3b 65 83 00 01 RIP [<ffffffff813ca6c8>] __nf_conntrack_find+0x53/0xb1 RSP <ffff8801b92c5768> CR2: ffff8805f74c8598 ---[ end trace d624218af5f5f65a ]--- Kernel panic - not syncing: Fatal exception in interrupt Pid: 3226, comm: qemu-kvm Tainted: G D 2.6.33-rc5 #1 Call Trace: [<ffffffff8143a899>] panic+0x7a/0x142 [<ffffffff8143ed83>] oops_end+0xb7/0xc7 [<ffffffff8102f719>] no_context+0x1fc/0x20b [<ffffffff8102f8ba>] __bad_area_nosemaphore+0x192/0x1b5 [<ffffffff8107a4db>] ? trace_hardirqs_on+0xd/0xf [<ffffffff8102f8f0>] bad_area_nosemaphore+0x13/0x15 [<ffffffff81440875>] do_page_fault+0x159/0x2aa [<ffffffff8143e0f5>] page_fault+0x25/0x30 [<ffffffff813ca6c8>] ? __nf_conntrack_find+0x53/0xb1 [<ffffffff813ca6b0>] ? __nf_conntrack_find+0x3b/0xb1 [<ffffffff813ca759>] nf_conntrack_find_get+0x33/0xb7 [<ffffffff813cb810>] nf_conntrack_in+0x209/0x7d0 [<ffffffff8140f2b3>] ipv4_conntrack_local+0x40/0x49 [<ffffffff813c85c9>] nf_iterate+0x4d/0xab [<ffffffff813da338>] ? dst_output+0x0/0x12 [<ffffffff813c869f>] nf_hook_slow+0x78/0xe0 [<ffffffff813da338>] ? dst_output+0x0/0x12 [<ffffffff81069602>] ? autoremove_wake_function+0x24/0x39 [<ffffffff813db42a>] __ip_local_out+0x8b/0x8d [<ffffffff813db442>] ip_local_out+0x16/0x27 [<ffffffff813dba70>] ip_queue_xmit+0x30e/0x36e [<ffffffff813ed9c8>] tcp_transmit_skb+0x707/0x745 [<ffffffff813f003a>] tcp_write_xmit+0x7cb/0x8ba [<ffffffff813f018e>] __tcp_push_pending_frames+0x2f/0x5d [<ffffffff813e2dab>] tcp_push+0x88/0x8a [<ffffffff813e50cc>] tcp_sendmsg+0x760/0x85b [<ffffffff8139b42c>] __sock_sendmsg+0x5e/0x69 [<ffffffff8139b742>] sock_sendmsg+0xa8/0xc1 [<ffffffff81111999>] ? fget_light+0x57/0xf2 [<ffffffff81111940>] ? rcu_read_unlock+0x21/0x23 [<ffffffff81111999>] ? fget_light+0x57/0xf2 [<ffffffff81140cca>] ? eventfd_write+0x94/0x186 [<ffffffff8139b7d2>] ? sockfd_lookup_light+0x20/0x58 [<ffffffff8139d497>] sys_sendto+0x110/0x152 [<ffffffff81110670>] ? fsnotify_modify+0x6c/0x74 [<ffffffff81118ddf>] ? path_put+0x22/0x26 [<ffffffff810a1671>] ? audit_syscall_entry+0x11e/0x14a [<ffffffff8143cf2a>] ? trace_hardirqs_on_thunk+0x3a/0x3f [<ffffffff81009bf2>] system_call_fastpath+0x16/0x1b [drm:drm_fb_helper_panic] *ERROR* panic occurred, switching back to text console Rebooting in 30 sec Jon. -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html